Four patients who had stenosis of a single major coronary artery which was treated by percutaneous transluminal coronary angioplasty are described. Three had exercise induced myocardial ischaemia complicated by ventricular tachycardia, fibrillation, and sinus bradycardia, respectively. Asystole developed in a fourth patient who had spontaneous chest pain. After successful percutaneous transluminal coronary angioplasty these arrhythmias did not recur spontaneously or on treadmill exercise testing. Percutaneous coronary angioplasty can be effective in preventing arrhythmias complicating acute myocardial ischaemia secondary to stenosis of a single major coronary artery.